Artificial denture



June 3, l R J. DONAVAN ARTIFICIAL vDENTURE Filed April 17, 1951 4 Sheets-Sheet l June 3, R. J. DONAVAN ARTIFICIAL DENTURE Filed April 17, 1951 4 Sheets-sheet 2 INVENTOR. P05527' J O/VV/V,

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June 3, 1952 R. J. DoNAvAN ARTIFICIAL DENTURE 4 Sheets-Sheet 5 Filed April 17, 1951 June 3, 1952 Y R, J. DONAVAN 2,598,769

ARTIFICIAL DENTURE Filed April 17, 1951 l 4 Sheets-Sheet, l

my f 96 f4 ,/f 1% i IN V EN TOR. @05E/P 7' J. OO/V4 V/V,

Patented June 3, 1952 UNITED STATES PATENT OFFICE ARTIFICIAL DENTURE Robert J. Donavan, Mason City, Ill. Application April 17, 1951, Serial No. 221,415

` This invention appertains to improvements in artificial dentures, either anatomical or mechanical, and has reference more particularly to the construction of false teeth as used in artificial dentures, either in the form of a whole plate, partial plate or bridgework.

The primary object of this invention is to provide articial dentures, which have approximately the same grinding and cutting efciency for food mastication as that of natural teeth, due to the design and construction of the occlusal surfaces of the molars and bicuspids.

A further object of this invention is to obtain maximum cuspal or ridge contact between the occlusal surfaces of the posterior teeth of the upper and lower dentures, the maximum contact permitting proper mandibular movements (anterior-posterior and lateral excursions) with a minimum of cuspal interference.

A further object of this invention is to improve the cutting and grinding efficiency of the occlusal surfaces of the teeth of artificial dentures by providing unique mechanisms on the occlusal surfaces of the molars and bicuspids and by providing a more extensive horizontal occlusal surface for the posterior teeth.

A further object of this invention is to provide armoured cusps on the occlusal surfaces of the posterior teeth, the armoured occlusal surfaces reducing to a minimum the wearing away and breakdown of the occlusal surfaces of the teeth and preventing loss of vertical dimension, especially in plastic teeth, while also preventing the chipping of the teeth or breaking up of portions of the cuspal walls, especially in porcelain teeth.

Still further objects of the present invention reside in the details of construction of the individual teeth and in the construction and relationship of the occlusal surfaces of the upper and lower posterior teeth which insures their greatest biting and masticating eiiiciency, and the least possible likelihood ofv cuspal interference, incident chipping of the teeth or displacement of the plates from proper position within the mouth and prevents an imposition of deleterious strain on the mucous tissues or imposition of direction upon the mandibular motion.

These and ancillary objects and structural features of merit are attained by this invention, the preferred embodiments of which are set forth in the following description and illustrated in the accompanying drawings, wherein:

Figure 1 is an occlusal surface view of upper and lower artificial' dentures including teeth constructed in accordance with the principles of the present invention;

Claims.

2 Figure 2 is a fragmentary perspective View of the posterior portions of one side of the upper and lower dentures, from the lingual side with the dentures in occlusive relationship;

Figure 3 is an enlarged perspective view of the posterior teeth on one side of the upper denture with the teeth shown in inverted position;

Figure 4 is an enlarged perspective view of the posterior teeth on one side of the lower denture;

Figure 5 is a transverse cross sectional view taken on line 5 5 of Figure 3 and illustrating the first molar in cross section to more particularlyl depict the cuspal arrangement and formation of the occlusal surface;

Figure 6 is a transverse cross sectional view taken on line 6-6 of Figure 3 and illustrating in cross section the first bicuspid, the cuspal and ridge formation being shown in detail;

Figure 7 is a transverse cross sectional view taken on line 1--1 of Figure 4 and illustrating more particularly the bucco-lingual ridge formed on the occlusal surface of the first molar;

I Figure 8 is a transverse cross sectional view taken on line 8 8 of Figure 4 and illustrating more particularly the formation of the occlusal surface of the first bicuspid of the posterior teeth of the lower denture;

Figure 9 is an occlusal surface view of an upper and a lower artificial denture of modified form in which the occlusal surfaces are formed with armoured cusps;

Figure 10 is an enlarged perspective View of the mating occlusal surfaces of the molars of the upper and lower artificial dentures;

Figure l1 is a transverse cross sectional view, showing more particularly the engagement between the cusps of the upper and lower molars;

Figure 12 is an occlusal surface view on an enlarged scale of one of the molars of the upper denture, illustrating in detail the arrangement and formation of the cusps;

Figure 13 is'a fragmentary occlusal surface view of one side of the upper denture;

Figures 14, 14a and 14h are cross-sectional views, illustrating in diagrammatic form the relationship between the upper and lower dentures, when in position in the oral cavity and during masticating movements to depict the `relationship between the occlusal surfaces, during mandibular motion, the denturesv being shown in concentric, protrusive and extrusive positions;

Figure 15 is an occlusal surface view of a posterior tooth of the upper denture having a modified form of cusp arrangement;

Fora more lucid understanding of the present invention, it will be generally recognized that articial or false teeth, in the form of the whole denture or plate, are relatively low in efficiency for the mastication of food, when compared with the high degree of eiciency of the full set of natural teeth. The comparative low efiiciency of the average set of dentures is essentially due to the anatomical aspect of the teeth, since, for estheticffreasons, those skilled; inthe prosthetic art have made false teeth to resemble as nearly as possible natural ones. In the provision of;

such false teeth, insuiicient considerationex;` Y

tended to the eiciency of the teeth during mastication of food. Whereas natural-teeth;agressecurely set in the bony structure of the jaw and, therefore, havela very high pressure range',V arti.-

cial teeth, on the other hand, must findtheir bearing surfaces upon the tender mucous tissues instead of in the bony tissues and ddnot have Sincefiieldelwree must, occupy. the Seme. position, as nearly as possible,Y the oral cavity,

necessarily'be'liinited-to the'posterior teeth, duev tofthe' thatzthefanterior teeth Yare visiblfA to the casualv glance of a layman and, for esthetic, reasons, should have anaturalappearance, Fur-v therr'nore,v the'posjierior teetharefof'greater importaein the :masticationjJ of' food". than theY anterorfteeth jandfthe; improvement therein to increase grinding o r crushing enficiency of the teeth 'with a more natural-movement or the Inaudible o 'r jaw isf. the instant-invention Iii-accordance with the object -ofthe instant invention, the cutting .`Aed ire s v of' the posterior teeth! 'or the dentures rare' improved, while' con-L siderati@ alSQ extended ,tQ`,^tl.le..preve.I1iQn. Ofi interferencebetweenV the occlusal js urlfjaies V of y teeth of the oppositedenturesnan to ,the obviation of interference with Amandib is, therefo'r'efthe `rirnaryjL a instant invention to providesubstantillyf the natural"- teeth 'for food masticatiqon by improving the designfand constructie ofjthe molarsf and bic'uspidf. the' artialzderturesf can'be appreciated, it is impossipleto estab- Yiish xed Ipath'sf f! movementffp; mandrel@ ac tion, since the actions'ofwthe mandihle'- during mastication vary considerably in Aeach'pe'rson.v In each individual, 'thefpaths of nOon of the mandible are-controlled byvarious factors' and articial 'denturesVV ini-isti beV constuctd'to Ycon?V i form to; the .corresponding path! 'o fi movements,

rather than tofsetI plandestablish airadically' diierent path of vfmoveme'nt; which, of course,

would. result; inl considrable 4interference y'wi-tnj the mandibular `actio`n and` would causefdelefterious strain oni the',jawsiandgumtissuesr The artificial dentures,l provided! by this invention, do not interfere.withithemoverent-of the man-f dible anteriorly, posteriorlyA oj' ,lateral,lylatanv angle, though 'ai sliglitV interference with; the

i prirria,ryl purpose of the..

A. rfmQtion; It. andpurposeo the.

. therefrom in use anditne teethshduidgyofe or space VcontainingI the.,A cusps. and, the.. si

mandibular is encountered in a downward slanting motion, in its lateral movements. However, the latter interference is natural and does Vnot work any strain on the niandible.

The foregoing object is accomplished by providing a multiplicityof cuspal and ridge contacts, the mandible moving freely, Without being locked by inclined planes of opposing cusps or guided into preconceived paths by grooves' or'other mechanical devices on occlusal surfaces.

More specically, the number of cusps on the premolars and molars of the upper dentures or platesvare increased and the cuspal and ridge de signof` the bicuspids and molars of the lower platesV arechanged and extensively modied, especially with reference to the provision of a novel buccolingual ridge structure. Furthermore, the cusps of the upper multi-cusp teeth are of rounded, partly globular form and the arrangement is modified so that slidingr Contact Withtheocclusal surfaces of the lower posterior-. teeth canbe effected.v

Referring. now moreparticularly, to the draw,-r ings, attentionis directedv to Figurel. whereth'e upper and lower platesffor'. dentures areillusf trated in plan viewjthe dentureshavingteeth set therein whichare made in accorda'neewith. the details and 'objectsoi .thejpresent invention The upper Vplate Il), andthe lower plateI I2.may f be molded in the usuall manner, and/may be. formed of any of theinaterialsnow ingeneral, use and the teeth whiharefsetin platesma'ybe of porcelain, or a molded material, such, asv acrylic or any other plastic, 'which wo'uldbe Satisfactory from a pointof durability, eiiiciency. color and capability of.' being4 molded tdV desired, shapes.

The manner. of forming theplatesandteeth, is immaterial, exceptithatl the teeth should'be permanently. unitedgwith the plates,j so'A Sisto, avoid any possibility, of; their displac ent be set in accordance. withythe,naturaLtootharf rangement of the patient, 'the jsize a,nd slr1 a p e of the teeth being determinedjthereby,

In Figurey 3, thejqcclusaljsurfaces for?. the bicuspids and molarsofithe, upper plateljisril, lustrated in detail, the o colvusall surfacesc "the, posterior teeth 'IE and I'Ggof the. upper .pl

structed in 'View' of Vthewsarre 'princip T anterior teeth Sjmasbe, `forinedfin,the` cpnve A tional manner. and s119111@ ,resemble as, nearly, possible, the natural-teeth ofjthe.patijenMt V The occlusal surfacesv off the. i"i rsi'. b i ci 1sp i.c 1 jl8A and. the SecondY bicilsgidiwlare. similare termed.. as al'rerthe olllllrfcs. -Of'tlQ-,ltfm '.-l 22 and. the. Seqomimglarli; Theocclusalsn faces of these' teet lj i .areisoconstruct/j f contain a group `o fgm'echaifiial,sen-1' semi-cylindrical cuspsi 2 61 cusps ,arejprovidedjor the.v bic-.USR fqalidll), and seven cusps. for the. first ,andf'secondQmclarsg 22 and 24,. However, anygnumberjof/f be formed, dependent upon ,'thejsizfe.. of..

the cusps. The number vnfsizpeffo'f v.tl1e'. .cus not of critical ,importance-aj, butQthe 'sha specific formation; and.v arrangement thereofzon',

the crown of the. f teeth constitutes.. one/of, the. important aspectsof this,..invention..

The area containing thecuSps ,isgdeiinedbn the buccal .side AV28A ,and ,on :the lingual side, 3Q by .buccal cusps4 32andlingualcllps.f34gwhich axel,A

of Vnatural design. From the buccalaridfl aspects, the buccal and lingual surfaces present the same contours, grooves,4 elevation and angles as natural teeth. vOn the mesial and distal sides, the molars are defined by the mesial marginal border 36 and distal marginal border 38, the bicuspids being similarly formed with distal marginal borders 40 and mesial marginal borders 42. The mesial and distal marginal borders of both the bicuspids and molars are so constructed as to be well below the tips of the cusps 26.

The occlusal surfaces of the bicuspids I8 and 26 are defined by the lingual cusps 44, the lingual mechanical cusps 46, the central mechanical cusps 48, the buccal mechanical cusps and the conventional buccal cusps 52. The semi-globular cusps 26 are so arranged that the lingual mechanical cusp 46 lies adjacent to the lingual cusp 44 and the buccal mechanical cusp Y 50 is disposed adjacent to the conventional buccal cusp 52, the cusps 46 and 50 being in a position so that they are intersected by the bucco-lingual ridge. The natural cusps 44 and 52 and the mechanical cusps, grouped in a specifically arranged pattern within the natural buccal and lingual cusps, are so arranged that when viewed from either the mesial or distal side of the tooth, the buccal cusps 52 are of the greatest height, with the conventional lingual cusp 44 being next in height. The buccal mechanical cusp 56 is third highest, with the lingual mechanical cusp being fourth in height and the central mechanical cusps 48 lying well below the plane of the tips or crests of the buccal and lingual mechanical cusps 50 and 46.

The elevation or arrangement of the cusps can be particularly discerned from Figure 6, wherein it will be noted that the conventional buccal cusp 52 is substantially higher than the conventional lingual cusp 44, with the buccal mechanical cusp 5D lying below the conventional buccal and lingual cusps and lying above the lingual mechanical cusp 46, which extends above the central mechanical'cusp 48.

The occlusal surfaces of the molar are constructed in a similar manner, in that the lingual cusps 54 and buccal cusps 56 are substantially conventional in formation, the conventional buccal cusps being the highest cusps on the occlusal surface of the molars and lying above the lingual cusps 54, as seen in Figure 5. The pair of buccal mechanical cusps 58, are next in height and lie below the lingual and buccal cusps. The lingual mechanical cusps are formed in a manner similar to the formation of the buccal mechanical cusps 58 and lie below the plane of the buccal mechanical cusps, the cusps 56 and 60 following the slanting pattern of the conventional lingual and buccal cusps and being arranged with the central mechanical cusps 62, which are the lowest cusps on the occlusal surface, so that the tips of the cusps lie on the arc AB, viewed from the distal side of the tooth and the line A-B being struck along the bucco-lingual ridge. Similarly, the tips of the cusps for the bicuspids, as seen in Figure 6, lie so that they are in an arcuate pattern.

As seen in Figure 13, the cusps of the premolars and the molars are arranged, so that the buccal mechanical cusps of the molars and bicuspids are intersected by a straight line A-B', which is extended in a distal-mesial direction. The central mechanical cusps are intersected by a line ACL-B, which parallels the 'line vA'-B' buccal and central mechanical cusps are thus arranged along straight parallel lines, A-B',

A-B and,A3--B3. the parallel lines being in .relation to theanterior-posterior motion of the .mandible and showing the arrangement of the mechanical cusps in relation to anterior-posterior motion, from the arch X. The position of the plate, as illustrated in Figure 13, in the oral ycavity will position the mechanical cusps along straight spaced apart lines which are substantially parallel -to each other, the intersecting .lines Y-Z showing the arrangement of the cusps for lateral motion.

In Figure 12,*the occlusal surface of the molars,

`is more clearly illustrated, the buccal mechanical cusps 60 being formed in a pair 60', 6l, Each of the cusps of the pair is spaced apart and is of the same height, the height of the cusps, in relation to the other mechanical cusps, being greater, While the three central mechanical cusps 62 are the lowest, on `the occlusal surface. The central mechanical cusps 62, 63 and 63' are of the same height, with the lingual mechanical cusps 58 and 59 being slightly above the central cusps 62 and slightly below the buccal cusps 6U. The buccal cusps are arranged in a pair, each of the cusps being aligned from a bucco-lingual direction, with the lingual mechanical cusps.

The cusps 58', 6U and 62' of the buccal, lingual and central mechanical formations form an arcuate broken ridge OP, on the mesial side of the tooth, while the cusp 63 forms, with the distal marginal border, a broken arcuate ridge M-N, the center H and B of the ridges being in alignment on the line A"-B", which parallels the anterior-posterior direction of movement of the mandible. The cusps 553, 63 and 6I form a broken ridge D-F, with the center E on the line A-B and the centers of the ridges being at the centers of the central mechanical cusps. The cusps of the -bicuspids and the molars, as depicted in Figure 13, lie on the parallel straight lines and the cusps of each individual tooth are disposed on the arcuate lines to dene the broken ridges across the occlusal surface of the tooth. The tips of crests of the cusps make sliding contact with the occlusal surfaces of the lower posterior teeth and carry the weight of occlusal contact and mandibular movement, (lateral, anterior and posterior) in all directions and at all angles, without forcing the mandibular into any preconceived paths.

In Figure 15, a modified cusp formation is illustrated, wherein the ridges 64, 66 and 68, lying on the arcs OBP, DEF and MHN, are unbroken. The individual cusps are illustrated in dotted lines but the ridges are unbroken instead of broken, as in Figure l2. A tooth, constructed as illustrated in Figure 15, would make the mandibular movements smoother and would have a better sliding engagement with the occlusal surfaces of the lower posterior teeth, due to the absence of sulci between the individual cusps and extending from the mesial to the distal side. All of the posterior teeth of a denture could be constructed in this manner or only the first molar may be so constructed, the first molar forming the bearing tooth for the teeth. The specified height relationship of the mechanical and conventional lingual and buccal cusps would be, of course, preserved, with the portions of the ridges, lying between the cusps conforming thereto.

I As seen in Figure 16, which is a crossrsectional deiiediiytiel-eusns r lingual nieehamel. and bueallineehanal Y sets with 'the spage'fhetween the 'cusps l'ldinf Y and `properly dimensionedand leveledifso toretain the saine elevational `relationshipl between the eusps,4 as illus"- trated rFigure 5. fihusfthe ousps'ql, GABfa/n'd f sa; which 11e on the 4me DEF. afrim emersa@- elevational interrelationship Aand relationship with the conventional )Queria-1 ei`1zp`s34 v-ar1 li ::-n ventional lingual -eueps 3 2.` Y

In Figure '1-1,` the upper niolag' 22 -iefshown in Vcross section; from a line -tran'eyerse to the anterior-poeterior direction of --1tnoifen1ent efthe -mandible and l*the araneement 'ofthe cuswpe with -respeetto-the1bucealsu1face offtheniola en Y v the lower denture can ibe `eenertained! theline -C-B showing the inelination -ofthe/ungerand 'lower teeth, Lfrom fthe verticalplane Attentionis lnow Ydirecteditcilifie'llljtil '4 rand the sectional illustratione, taken from -Figure 1., wherein the posteifior teeth {j'lpof the lotti-'er denture are Yilluslti'ate'dV L'including thepairef-pre molers or vbicu'spids "#2 and'2 1 4' and the iiist and second `Inolars 1B and- 1758# l'The occslusel @supi-aces `ofthe lower bicuspids and-inplaats have beendesigned and oonetruetdlfor properengagement,

Lwithout -cuspal Yo1" ridge interfrence, with lthe cuepe on the poste'riQr-teethofitheupper denture or eplate. The bieuepids'fl langl- 1'4-are folgmed =buceolingually by messia/e sized tenace-lingual -ridgee BWI) and'Z, the ridges being fof af Vsize -to 'or crests! of l the -multi-eusps en the -eeclusal` suie- Teces of the Aupper posterior eteeth, '-so Ythat a smooth and yieldingfpassa'ge tdtheJmandlbular -action is-previdedi- "Plie-bieuspidsandmolars of uthe -bottom plate or dentunefvyhen viewediffom al buecel Vof lingual idiree'tio'n,l -pijesent lthefsaine eontours,grooizes,elevationalfi'danglesfasV anatu- -ral tooth. v"Theirst-ariglseeondeleiuspids FM and 'l2 are -ioiemed-with `l`the distinctelingual cusps 84 'The bucoal euspsiSZ and the:1irigua1cuspsi94 4on the Vfirst andfseeen.lgido-larsy are d efnedlbyjthe ieuocal` andlli-ngual-4 grooves-and.- depressions V(mithe buccal and lingual surfaces, with thelligu'al-cu'sps being reduced in size ascoinpared withthefbuoeal Both Vthe fbuecal- :and ilingu-al .ouspsf are `95 extending from-the -mesia1=tofthe.distal enz-the buccal and ling'ualisides of the?oirsclusr'alasu'ifece'slv i the ridgesireplacingthe eusps..and being massive in design. I-he .-buocal .and :flingual iidgeSL-are united hy the nassive bucco-lingual. ridge cgfon the occlusal surface .of...eaoh.mo1ar, c:the i bucco; lingual ridgev vcrossing -the occlusal.surfaes in .a bucco-.lingual v"diectionf slightlyd mesial .to the i buceoelinualaxisficifthefoccliusiel.surilaoes.

The point of.v emmnceforlthe ocl-us'alfisurtaees of the vsecond'-bie'uspid' and; therst andls'ecozid Y molars; is located on the hueeoelingualridgsp; v96 Vand 198, `on the V4mes'ia-l-distel Lcenten.` of the i bucco-lingualridgeslightlbucalrtthelmsial iionsepimyfmesieninandusually-t6@mythe meeiei eee. diste! eeiei eyte..ii.1.e.. eee. .Slightly buecelly end ylingueily te ferai .tile .eieet .Qf ille "Theeeeieei'eeieetithecleueixeteieueeie :ie iseiiierent .trete thee .ef .tile .seeensl isieee'pid eee. tiret end. eeeend ingiere .iriemeeii ee the peiijit et eminente 102. .eti hej :tie ef the iidee'tfteeeeeeiii-.Eieeee side'. '-,lhebuece-lineelridge te ereeeee -face in a lbucco-lingual direction from the high .Peint eiiteiidingv @emit/ere .te .the .eeiiter ef .the Serfeee. Wiiere'it. ieerqeeed les' .tile .eleniieeetine eiileee. lefty-ee .seensiii rieure @..tiie .spleet termine meeieily. eefleietgeiiy te milite the v:tive suloi systeme H13 and l 11,8.

.It ecill v'te .iiet'ed .tiiet 'tiiejpliieh peint. ...en .tile 'eeeeelineiiei riileesef .the 99-11 leerte. eef 'thebieee'iiide end. meters ef. trie.n .teeth .ereiiiglier than m eeeieeel eurieeee Theep eiiieieiin bueee-.lieguel ridges. .witiitiie .peint ef .eminente of thle eeeiueeleurfeeefeimed tiieeeemeeeisteie gli/ ing a downward elanting direeti erel. .meteitieiit .ef :the .m

-ieeeted .en theiere et ell' sii. .eeglee .Tile melti-euseteethei .tiieeeeer ereh .meetthe mei-.Selva ridges .teeth Ain .tip dto tip. multiplie y @etten with' ieee. heim' :te tite .uiideleinsfee'ft miieeiie-.tieeeee 21nd... i. Strutture-e :Tfn ti "leetweentheecteeth.. will. be. .e ...eeeteet .te .the

crushing eed..ieterleekeemeetieg-.ef .the .mere

er leeefiet .inelined nien .eitheleieee eti-.the .eementienel .teeth- .'Iiieeneleedeleiie-eef. the .euepeef .ceriventienei .ethfneeeeiitereet iiiteiefereneetaleterel.mend. ..,emetieitendfinedeie tieietenete .imrieee elreetiee .elette eeet. deif .niteuiethe .Qf-eeuree. reumied-eurieeee een-,pees leere.. readily .over geeeh. Qtiier ...there .merle t er less...iiet Surfeees end Sinee-.tliecenteet-surieees .ef..tlie't.e,et.1i ef this inve-ntie@.-eretreuiided,.end Y peint ef eiiiieeiieetll?.

.endeeeeiie bieiispidel endl? lieve the distinct buccal and lingual cusps 88,l 84, 86 9?.- .Tlieeuepeeee-blunt and .meseiveend riety leigh er.. i Sheep. with v.the -liiieuei .ei1ee..;beii1.s' metil. Smelleitlielirthe.bueeeleuslie eliieel. ,Seriate ie .f eeeefii. .eieiieee tieiilextiie heeeeflmeuel rieieee.-

'1 'thejdentereglifthe .first eeeeeeesideieeeef rienteeth are. Seerl.ranged that the lingual cusps 84 and 86 are free from contact with the multi-cusp occlusal surk faces of the rst and second posterior teeth of the upper set, when the mandible is in anterior-posterior or lateral motion. The contact of the first and second biscuspids with the upper posterior teeth is on the buccal cusps and the bucco-lingual ridge of the second biscuspid. These blunt cusps and the massive ridge bear the weight of contact with the multi-cusp upper posterior teeth at many points and permit the anterior, posterior and lateral excursions of themandible with a minimum of cuspal interference. The buccal ridge 92 is much larger than the lingual ridge l94 and occupies a position of slightly greater height. The buccal and lingual ridges are made in more or less the shape of a segment of a cylindrical body from the mesial and distal aspects. These massive buccal and lingual ridges, of more or less cylindrical shape, when in Contact with the multi-cusps occlusal surfaces of the upper posterior teeth, present a multiplicity of Contact, which reduces cuspal interference to a minimum in the anterior, posterior and lateral excursions of the mandible. The massive bucco-lingual ridges of the second bicuspid and rst and second molars, on which are the high points of these occlusal surfaces, presents a slanting downward direction to the motion of the mandible in its lateral excursions and assists greatly in anterior and posterior movements.

The first bicuspids, the second bicuspids, and the first and second molars have two distinct sulci systems, mesial and distal. The sulci systems of the first bicuspids are different from those of the three other teeth. In the rst bicuspids, the bucco-lingual ridge 8B is crossed in a mesial-distal direction by the connecting sulcus at the lowest point on the ridge, the sulcus falling rapidly downward to the mesial and distal to form the mesial and distal fossa. A mesial-lingual and a mesial-buccal sulci is dened by the fossa and a distal-lingual and a distal-buccal sulci is defined, the sulci descending slowly to their termination at the distal and mesial borders of the occlusal surfaces.. 'Ihe occlusal surface of the first bicuspid presents only two fossae, a distal fossa, and a mesial fossa, the sulci from their source descending downward in all parts of their course.

The second bicuspid and the rst and second molars have two distinctsulci systems on each occlusal surface, the sulci systems being separated by the bucco-lingual ridge. The sulci systems are alike except that the distal systems are somewhat reduced in size, so that a description of one should be suicient for all. For example, the mesial sulci system of the occlusal surface of the iirst molar is as follows:

The sulci system takes its origin from two points, one buccal to the mesial-distal axis of this surface, the other lingual to it, at the junctions of the bucco-lingual ridge with =buccal and lingual ridges. From these points, the sulci extend downward and mesially to the mesial-distal axis where they form a junction, just lingual to the axis (the junction being the mesial-central fossa). This junction is the inception point for a single sulcus to the mesial and downward to form the mesial fossa, which defines two sulci downward and to the mesial-lingual and -mesialbucca1 to their termination at the mesial border. The sulci system from its origin to its termination always pursues a downward course, the sulci forming four fossae on the whole occlusal surface as follows, the mesial fossa, the mesial-central fossa, the distal-central fossa and the distal fossa.

Thus, in the posterior teeth, the occlusal surfaces are formed, so that there are four fossae on the occlusal surface of each tooth, except the lower first bicuspid has two fossae, and the buccolingual ridges are formed, so that the high point of eminence is in the center of the ridge and the point of eminence denes the highest pointl on the occlusal surfaces of the bicuspids and molars. The buccal and lingual ridges are formed, so that theirl crests are contoured throughout their entire lengths, or the crests being in a straight line 'and contoured slightly only at the ends.l The sulci j movements of the .mandible vary in each person and are governed and given their course by things and conditions that are peculiar to each individual. Thus, muscles, fossa bone structure, tissue toleranceand many other factors enter into the initiation and determinence of the course and movement of the mandible. Every indivi-dual has anterior, posterior and lateral movement of the mandible and all ydentures are constructed, ywith themovements of the mandible in mind.

In Figure-14, the upper denture plate Id and lower denture l2 are illustrated in centric position, the molars 16 on each side of the posterior teeth being illustrated, with the bucco-lingual ridge exploited. The molars of the upper denture are illustrated in cross section. The dentures are depicted in centric occlusion parallel to lines CD and CD which illustrate this position in all of the figures. At |00, the point of eminence on the bucco-lingual ridge of the molars of the lower posterior teeth is illustrated, the point resting directly under one of the mechanical cusps of the upper molars. Thus, in Figure 14, the point of eminence is directly in vertical alignment and underlies the crest or tip of the mechanical cusps 632 so that the point E overlies the point of eminence of the ybucco-lingual ridge, the arc DEF transversely intersecting the point of eminence at its center. The three central mechanical cusps 62, 63 and 63', as seen in Figure 12, are constructed on each molar so that the buccolingual ridge on the lower molars must be in contact with one or more of them at all times `in centric relation. The bucco-lingual ridge of massive proportions must be large enough to span or almost span the distance between the cusps on the upper molars. The larger and more evenly contouredthe bucco-lingual ridge is, the moresmooth will be the mandibular movements. The arc KL illustrates the plane in which the crests of the upper cuspslie. Each of the upper molars is formed with 11 cusps, which ideally should'all contact the ridges of the lower molars but, due to imperfection in skill and materials, usually only 8 of the cusps will' contact the ridges of the lower molar, but, in any event, a multiplicity of cuspal and ridge contact is provided, whereby the occlusal surfaces can pass freely over each other without greatly disturbing interference in mastication.

n anterior-posterior movements, the ridges of the lower teeth would pass freely back and forth contacting the multi-cusps within the arc KL. However, anterior motion would be disturbed the instant the incisal edges of the llower anterior teeth began to mount on the lingual surface of the upper anterior teeth. At this point, balanced occlusion is lost and malocclusion begins and only the retention of the dentures against the underentame.

lying mucous tissue holds them in place. PosteriorV nence on the bucco-lingual lridge kbe'ing'mmfed to the right to gain contact with the buccal mechanical cusps .and possiblyy to the conventional buccal cusps. YOf course, the 'latter'movementjis dependent upon therange of lateral movement and Ythe .range ofrlateral 'and Yanterior-posterior movement varies greatly in different individuals.

On the opposite side of thedentures, the :point of eminence .|20 is moyedto'the right to contact the lingual mechanical cusps 6.6 andthe 'lingual conventional ousps 54. The'whole ridge surfaces of the lower Aposterior.teetl'i will Ibe in contact.

with the crests 'or .tips of the vcusps of the upper teeth, the degree of contact being in vaccordance with the perfection of the 'tooth assembly-set up.

This gives a multiplicity .of contact whichV permits movement w-ith greatfreedom andbalanced occlusion the movements. At the same time that the lateral movement iscarried on,jthe crest of the bucco-lingual Vridge is in vcontact ywiththe A upper cusps and 'will guide the mandible lalong the arc A-B, in which the crests vof the upper cusps are located, the mandible being guided toa downward slanting direction in the lateral movement.

In Figure 14h, the Vleft lateral excursion of the mandible is illustrated, the laction being opg posite to the illustration in Figure 14a, since the cusps and the four conventional cusps. In anv terior and -posterior motion of the lmandible, the ridge because of its massive construction slides over the tips or crests of the upper mechanical cusps with great ease, being too ylarge and mas.-

. sive to fall inthe spaces between them and cause i interference. 'Moreoveig these occlusal surfaces give .extreme freedom to anterior and posterior motion of the mandible, as far as the `upper anterior teeth will permit. Interference in anterior and posterior Amotion in the Inaudible is due mostly to the Vlower -incisors and cuspids c passing forward and downward over the lingual surfaces of the six uppr anterior teethJ .causing the posterior teeth to 'loseocclusal contact with each other.

'Ihuajit `can be Yseen that the multi-cusp teeth will increase masticating eiiiciency, since a multiplicity of `cusps will beV formed on the oc-V clusal surfaces of the upper posterior teeth and l complementary ridges will be formed von the occlusal surfaces of the lower posterior teeth, .the

ridges mating in sliding and free engagement with the cusps on the occlusal surfaces 4of the `upper posterior teeth. The ridges on the lower posterior teeth take the place of cusps and perform the same masticating function and additional functions, such as increasingrthe ease of mandi'bular movements.

The following features are of extreme importance:

12 A. Multiplicity ofcusps on the occlusal surfaces of the upper posterior teeth and modified bucco-'lingual ridges.

B. Modified bucco-*lingual ridges on lower teeth for modifying ridge structures.

C. 'Sulci 4systems of the occlusal surfaces of Y the lower Ateeth@.differing from other sulci systems 'andthe fact that `from their source they extend downward in all parts of their course.

D. Uniquemechanical devices upon the occlusal surfaces of the vposterior upper and lower teeth to increase masticating efficiency.

`E.'The unique mechanical device .upon the Aocclusal surfaces to `reduce interference with Ymandibular motions. Y

F. A -minimumof guided direction imposed rupon mandbula-r friction, the imposed guided directionl'being only that of a downward slanting direction :to lateral movement.'

G. 'The natural appearance of the ,teeth from any 4reasonable area of visibility.

Itis *to 'be particularly noted that the buccolingual -ridges .are semi-cylindrical in shape and the ridges .extend ,from buccal to lingual surfaces in .an arc 'mesially or .distally or straight across as the size and shape of the occlusal surface will permit. The .bucco-lingual ridge or the lower teeth ismassivein design extending straight across the 'occlusal surfaces and dividing the surfaces into a mesial and a distal area, in which are the'unique sulci systems. The straight buccolingual course of the ridge and its point .of eminence for the flower occlusal surfaces aids in the j proper vmastication and in the movement of the lower dent-ure on lthe upper denture. y

'InFigure 9, modified denture structure is provided, the `occlusal surfaces vof the .posterior upper and lower teeth being armoured or capped. The purpose of Vcapping or armouring the cusp occlusal surfaces and the ridged occlusal surfaces on the upper and. lower posterior teeth is to prevent or. .to reduce to a minimum the wearing away of the occlusal surface, thereby preventing loss of vertical dimension.

The occlusal surfaces |24 of the posteriorteeth of the vupper vdenture are formed and constructed in a manner similar tofthe construction o f .the

thereon. 4The occlusal surfaces of the .posterior` teeth of the lower denture |26 are formed with the 4 ridge structure and the sulci, as in Figure 1, except that the ridge and sulci are covered with an armour.

It cangthus be seenthat the occlusal surfaces of theupper posterior teeth are especially formed with the cusps, -arranged .and constructed as aforedescribed, and the occlusal surfaces ofthe lower posterior teeth are especially formed with the ridge and sulci systems, so that the `QCClusal surfaces engage in sliding contact and .obtain proper mastica-tion, the loss of pressure, such as found in natural teeth, being compensated `for by the cutting and grinding action of the mating occlusal surfaces `of the upper and lower teeth. Also,y the vparticular formation of .the Vbuccolingual ridge and especially, the :point of .eminence thereon, lpermits proper mandible motion, without any interference and especially, without imposing any strain or wear on the gum tissues and' causing improper seating of the plates.

While the foregoing invention has been especially described and illustrated as related to dentures or full plates, it is apparent that the same can be used to full advantage with bridges or individual replacement teeth.

Having thus described this invention, what is claimed is:

1. The combination of upper and lower dentures, each having artificial posterior teeth, the posterior teeth of the upper denture having semiglobular cusps formed on their occlusal surfaces and the posterior teeth of the lower denture having bucco-lingual ridges extending across the occlusal surfaces and adapted to span the cusps on the upper teeth.

r2. The combination of upper and lower dentures, each having artificial posterior teeth, the posterior teeth of the upper denture having buccal and lingual cusps and semi-globular mechanical cusps arranged between the buccal and lingual cusps, the mechanical cusps on the occlusal surfaces of the premolars and molars of the upper denture lying in parallel planes parallel to the anterior-posterior direction, and the posterior teeth of thelower denture having buccolingual ridges formed on their occlusal surfaces and adapted to span the mechanical cuspson the upper teeth, said ridges defining distinct sulci systems on the occlusal surface of each lower tooth.

3. The combination of upper and lower dentures, each having artificial posterior teeth, the posterior teeth of the upper denture having buccal and lingual cusps and semi-globular mechanical cusps on the occlusal surfaces of the premolars and molars of the upper denture lying in parallel planes parallel to the anterior-posterior direction, and the posterior teeth of the lower denture having bucco-lingual ridges formed on their occlusal surfaces and adapted to span the mechanical cusps on the upper teeth, said ridges defining distinct sulci systems on the occlusal surface of each lower tooth, said sulci systems lying mesially `and distally of the buccolingual ridge and originating from two points, one of said points being buccal to the mesialdistal axis of the occlusal surface and the other lingual to the mesial-'distal axis.

4. The combination with upper and lower dentures, each denture having artificial posterior teeth, the posterior teeth of the upper denture having buccal and lingual cusps and semi-globular mechanical cusps arranged between the buccal and lingual cusps, and the posterior teeth of the lower denture having massive bucco-lingual ridges formed on their occlusal surfaces, the ridges each having a highest point which points define the points of eminence of the occlusal surfaces of the lower teeth.

5. The combination with upper and lower dentures, each denture having artificial posterior teeth, the posterior teeth of the upper denture having buccal and lingual cusps and semi-globular mechanical cusps arranged between the buccal and lingual cusps, and the posterior teeth of the lower denture having massive bucco-lingual ridges formed on their occlusal surfaces, the ridges having a highest point which defines the point of eminence of the occlusal surfaces of the lower teeth, the point of eminence of the occlusal surfaces of the lower teeth being above the buccal and lingual ridges of the teeth and being round- 14 ed for contact with the tips of the mechanical cusps on the upper teeth.

6. The combination with upper and lower dentures, each denture having artificial posterior teeth, the posterior teeth of the upper denture having armoured mechanical semi-globular cusps formed on their occlusal surfaces, and the posterior teeth of the lower denture having armoured lingual and buccal cusps and armoured buccolingual ridges adapted to span the mechanical cusps of the upper teeth during mandibular'motion.

7. In-a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and spaced apart mechanical cusps of rounded shape disposed between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a transverse ridge extending between the buccal and lingual ridges between the mesial and distal borders of the complementary occlusal surface, the ridges on each lower tooth having a width at least as great as the distance between adjacent mechanical cusps on the complementary upper tooth.

8. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and mechanical cusps of rounded shape spaced apart in both a buccal-lingual and a distal-mesial direction between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a transverse ridge extending between the buccal and lingual ridges between the mesial and distal borders of the complementary occlusal surface, the ridges on each lower tooth having a width at least as great as the distance between adjacent mechanical cusps on the complementary upper tooth.

9. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface transversely concave in a buccal-lingual direction and has buccal and lingual cusps and spaced apart mechanical cusps of rounded shape disposed between said buccal and lingual cusps, and each lower tooth has its occlusal surface transversely convex in a buccal-lingual direction and has a buccal and a lingual ridge and a transverse ridge extending between the buccal and lingual ridges between the mesial and distal borders of the complementary occlusal surface, the ridges on each lower tooth having a width at least as great as the distance between adjacent mechanical cuspsV on the complementary upper tooth, the buccal cusp on each upper tooth having a greater eminence than any other cusp on the same tooth and the lingual ridge on each lower tooth having a greater eminence than the correspending buccal ridge.

10. In a group of artificial posterior teeth including complementary upper and lower teeth having meeting occlusal surfaces, the construction in which each upper tooth has its occlusal surface'transvrsely concave :in a buccal-lingual Vdirection `and-has bu-ccal'and lingual 'vcusps 4and Verse *ridge zextending rbetween 'the buccal and lingual ridgesV 'between 'the mesial and distal borders of Vthe complementary occlusal Surface, the ridges on each lower tooth having 'awdth 'alt least as great as the distance between adjacent mechanical cusps on the complementary upper tooth, the buccal'cusp'on each upper tooth havinga 'greater Ieminence than any other cusp on the same tooth and the lingual ridge on each i lower tooth ha'ving a Igreater eminence than the corresponding buocal ridge 'with the point of maxits imum'emnence onvea'chlower tooth located on the buccal-lingualridges of ysuch tooth.

"ROBERT J. DONAVAN.

'R-FRNCES vOrrin) Y v The following references are Vof record in the file of this patent:

UNITED STATES PATENTS Number" lName Date 1, 3ef1g171 immer Feb. 1, 1921 1,987,132 Schroder etal Jan. 15, 1935 2,'5 4;9 56 Dickson Apr. 17, 1951 2,549,636 'Rber Apr. 17, 1951 IFRIGN PATENTS Number Country Date Great'isruain Aug. 28, v1901 

